The Risser sign refers to the amount of calcification

Calcification

Calcification is the process in which calcium salts build up in soft tissue, causing it to harden. Calcifications may be classified on whether there is mineral balance or not, and the location of the calcification.-Causes:...

 of the human pelvis as a measure of maturity.

On a scale of 5, it gives a measure of progression of ossification

Ossification

Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...

; the grade of 5 means that skeletal maturity is reached. Risser sign is based on the observation of an X-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

 image.
Grade 1 is given when the ilium (bone)

Ilium (bone)

The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

 is calcified at a level of 25%; it corresponds to prepuberty or early puberty

Puberty

Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...

.
Grade 2 is given when the ilium (bone)

Ilium (bone)

The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

 is calcified at a level of 50%; it corresponds to the stage before or during growth spurt.
Grade 3 is given when the ilium (bone)

Ilium (bone)

The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

 is calcified at a level of 75%; it corresponds to the slowing of growth.
Grade 4 is given when the ilium (bone)

Ilium (bone)

The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

 is calcified at a level of 100%; it corresponds to an almost cessation of growth.
Grade 5 is given when the ilium (bone)

Ilium (bone)

The ilium is the uppermost and largest bone of the pelvis, and appears in most vertebrates including mammals and birds, but not bony fish. All reptiles have an ilium except snakes, although some snake species have a tiny bone which is considered to be an ilium.The name comes from the Latin ,...

is calcified at a level of 100% and the iliac apophysis is fused to iliac crest; it corresponds to the end of growth.

External links

• http://www.e-radiography.net/radpath/r/risser-sign.htm